The invention relates to a method for producing a torsional vibration damper housing and, in particular, a housing for a viscosity torsional vibration damper having a working chamber, which is constructed in the damper housing, can be filled with a viscous damping medium and in which a seismic ring is disposed, as well as having a fastening flange for fastening to a rotating machine part to be damped. The damper housing is produced from an existing thick circular plate blank and formed in an impact extrusion machine by a non-cutting impact extrusion shaping method.
Viscosity torsional vibration dampers of the above-mentioned construction are known having multiple constructive designs. Likewise, various manufacturing methods are known according to which such dampers and damper housings, respectively, are manufactured. When producing the above-mentioned viscosity torsional vibration dampers (in the following abbreviated to “visco-dampers”), a housing body is generally formed, which comprises a working chamber for accommodating a seismic inertia ring and a viscous damping medium. The seismic inertia ring is disposed to be sliding with a limited amount of play in the working chamber. The remaining gap spaces between the seismic ring and the working chamber are filled with a highly viscous silicone oil as the damping medium. By means of a radially interior flange, the ring-shaped damper housing is screwed to a rotating machine part which is to be damped, as a rule, to the shaft to be damped. In most applications, this is the crankshaft of a piston engine, mainly a diesel engine, on whose opposite face the visco damper is mounted.
Originally, to the extent that they were to be closed-off by means of a welded-on or rolled-in lid, the housings of the visco-dampers were “worked” or manufactured out of a solid material, of preformed pressed parts and of ductile cast iron in a cutting manner, as known, for example, from FIG. 6 of German Patent Document DE 951 965. For economical considerations, the so-called thin-sheet housing was later developed. The thin-sheet housing was joined together from two deep-drawn sheet metal caps by means of electron-beam welding. International Patent Document WO 96/41974 describes such a two-part housing.
In order to reduce the working or manufacturing steps, early attention was also given to producing one-piece thin sheet metal housings produced by high-expenditure hydroforming, pressing and burnishing. This, however, resulted in a sparsely dimensioned flange thickness only when the lid was added. This operation is described by the state of the art disclosed in European Patent Document EP 0 423 243 B1. European Patent Document EP 0 503 424 B1 describes a damper with at least one molded-on ribbed V-belt track.
All of the above-mentioned production methods known from the prior art require high expenditures with respect to the machines and tools required for the forming of the above-mentioned thin-sheet metal housings. As such, the variety of visco-damper types that can be produced is extremely disadvantageously limited by the required high expenditures. The desire remains, therefore, to produce multiple housing shapes from simple circular plate blanks at reasonable cost. One step in this direction is described in the state of the art disclosed in European Patent Document 0 512 295, which describes the splitting of housing blanks in the form of circular plate blanks.
Based on the disadvantages indicated in the prior art with respect to the high expenditures for machines and tools for implementing a plurality of damper types, it is an object of the invention to produce, in a novel manner, a thick circular metal plate blank in a non-cutting manner in a damper housing with arbitrary dimensions and wall thicknesses differentiated according to the corresponding stress for a plurality of damper types.
In particular, it is an object of the invention to produce, by means of simple process steps and without a high-expenditure tool change, a housing body which does not have only one working chamber, but in a simple manner with the same process steps has additional pulleys or supporting collars and coupling elements.
According to the present invention, this and other objects are achieved by a method for producing a torsional vibration damper housing, in which, in successive impact extrusion forming steps, all parts of the damper housing projecting out of the plane of a circular plate blank, which forms the rear wall of the housing, are impact-extruded from the circular plate blank while reducing its wall thickness in a non-cutting manner to form a one-piece damper housing.
Advantageous developments and further developments of the invention are described herein.
By means of successive impact extrusion forming steps, using an impact extrusion roller and a mandrel body, the material of a thick circular plate blank is impact-extruded on both sides of the circular plate blank. In this case, the walls of the working chamber as well as additional pulleys, supporting collars and coupling seats are shaped-out by reducing the wall thickness of the circular plate blank due to the impact extruding. In a first working step, the fixing of the circular plate blank takes place on an impact extrusion machine. In a next working step, the pressing of the radially interior wall partially forming the working chamber, of the bearing block, from the circular plate blank takes place, beginning at a defined distance from its radial circumference by means of the impact extrusion roller acting against a mandrel body radially toward the inside. The elevation which is formed radially on the outside on the circumference of the circular plate blank is pressed by means of an impact extrusion roller against a cylinder sleeve and, while forming out the radially exterior wall extending at a right angle away from the circular plate blank, the outer jacket of the working chamber is constructed. On the surface of the outer jacket oriented toward the outside, by pressing the outer jacket against a pressing mandrel body, a profiled running track is constructed, particularly a so-called poly-V track for receiving a profiled traction device, and here particularly a ribbed V-belt.
By means of additional process steps, by impact extruding the rear wall of the housing on the side of the circular plate blank opposite the working chamber against an impact extrusion mandrel body from a radially outward to inward direction, a rearward pulley is constructed. As a function of the desired damper type, the displacement of the material volume on the rear wall of the housing of the circular plate blank takes place by means of the impact extrusion roller. This additional pulley, which is provided for receiving a traction device, is also profiled with a profiled surface, particularly a running track, while impact extruding the surface of the pulley.
In a further process step, by further impact extruding on the side of the circular plate blank situated opposite the outer jacket and the bearing block, a supporting collar and a coupling seat for receiving a torsionally elastically uncoupled pulley are constructed in a non-cutting manner, by impact extruding against an impact extrusion mandrel body. During the various process steps of the impact extruding, the wall thickness of the circular plate blank, which forms the rear wall of the damper housing, is reduced by displacing the material volumes into the housing elements of the various damper housing types respectively, which extend from the rear wall of the housing or the circular plate blank, as a rule, at a right angle.
The construction of the supporting collars by impact extruding the circular plate blank takes place from the radially outward to inward direction by impact extruding against an impact extrusion mandrel body. In this case, in a further process step, the coupling seat is thrown up against an impact extrusion mandrel body, in that an impact extrusion roller impact extrudes from a radially outward direction, starting after the supporting collar, radially inwardly in the direction of the center bore. This has the advantage that, in the area of the coupling seat (thus radially around the center bore), the rear wall of the housing has a larger wall thickness than in the other areas.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.